Technique for producing a fine grained dithered halftone image h

Details Technique for producing a fine grained dithered halftone image h Technique for producing a fine grained dithered halftone image h

1989-06-27

1991-10-01

Crosland, Donnie L.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358455, 358456, H04N 140

Patent

active

050538870

ABSTRACT:
A technique for producing a dithered halftoned pattern for reproduction on a binary printer having a limited resolution where the halftoned pattern has a relatively fine screen ruling and, for a given size dither matrix, can depict an increased number of gray levels. Specifically, with this technique, gray level error is propagated from tile to tile and based upon the total gray level value for a current tile, which includes both the gray value for that tile itself and the gray level error propagated thereto, one of a number of different threshold matrices is selected. The selected matrix is then used to generate a dithered halftone pattern within the corresponding tile in an output halftoned image in order to depict a desired intermediate gray level in a corresponding area of that image. The threshold matrices produce corresponding dither patterns that illustratively differ by one darkened pel. As such, the differing dither patterns, when appearing for example in an area of a uniform coloration within a halftone tone image and viewed by the eye of a human observer, are spatially integrated together to advantageously produce an intermediate gray value in that area that can not be produced through use of either dither pattern alone.

REFERENCES:
patent: 4547811 (1985-10-01), Ochi et al.
patent: 4654721 (1987-03-01), Goertzel et al.
patent: 4760460 (1988-07-01), Shimotohno
patent: 4800443 (1989-01-01), Crinon et al.
patent: 4823189 (1989-04-01), Haines et al.
G. Goertzel et al, "Digital Halftoning on the IBM 4250", IBM Journal of Reserach and Development, vol. 31, No. 1, Jan. 1987, pp. 2-15.
R. Ulichney, Digital Halftoning (London: The MIT Press, Jun. 27, 1989, pp. 84-98.

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